1. Field of the Invention
The invention relates in general to speed pattern generators, and more specifically to the digital generation of a speed pattern for an elevator car.
2. Description of the Prior Art
The car controller of an elevator car performs such functions as keeping track of car position and tabulating the calls for elevator service. It controls the car and hatch doors, it sets the car travel direction circuits, and it initiates a run of the elevator car to a target floor. It controls the hall lanterns, and it resets calls when they are serviced. The car controller also stops the elevator car at floor level, and it relevels the car when necessary. In addition to these functions which may be broadly called floor selector functions, it also generates a speed pattern for use by the motor controller portion of the elevator drive machine. While these functions have been performed in the past by relays, hard wire logic, and analog circuits, it is now desirable to perform them by microcomputer. The microcomputer requires little physical space, and it has a relatively low cost.
The relatively low cost of the microcomputer has resulted in segregating systems into functional sub-systems, and using a microcomputer in each sub-system. Thus, in applying microcomputers to an elevator car controller, the floor selector and speed pattern generator functions would each have its own microcomputer. This is especially true, because digital generation of a speed pattern by microcomputer involves time-consuming calculations which must be made at a rapid rate in order to provide the required precision and accuracy.
While microcomputers have a relatively low cost, each additional microcomputer used in a system adds to its cost and complexity. Thus, it would be desirable to be able to perform all of the car controller functions for an elevator car with a single microcomputer, if this result can be obtained without sacrificing the precision and accuracy of the speed pattern generator function.